Multiprotocol label switching (MPLS) is a connection oriented routing technique used in data networks for directing data from one node to a next node in the network based on path labels rather than network addresses (e.g., Internet Protocol (IP) traffic routing). Use of the path labels, instead of network addresses, avoids complex routing table lookups.
IP is a connectionless routing technique where routers route packets based on destination and/or source IP addresses. The forwarding decision at the router is made on a hop-by-hop basis without setting up a connection. In a connectionless routing technique, bandwidth typically cannot be reserved for a given packet session. In an IP network, each router routes each received packet by matching the destination IP address with entries in the routing table using a longest prefix matching algorithm.
MPLS, being a connection oriented routing packet forwarding mechanism, forwards packets based on a fixed-length, short label that corresponds to a label switched path (LSP) that has been previously established via signaling between an ingress and egress node in the network, and via intermediate nodes on the path between the ingress and egress nodes. Forwarding attributes (e.g., bandwidth) for the virtual link (i.e., label switch path) are typically negotiated during the connection set-up signaling. MPLS, therefore, introduces signaling overhead to establish the label switch path, but results in subsequent less complicated packet forwarding with less delay relative to IP.